Isolation and Cultivation of the Source Organisms of Long-chain Diol lipids from Marine Environments to test their Application in Palaeoclimate Studies

• Applicant: Dr. Sebastiaan Rampen
• Subject Area: Ecology and Biodiversity of Plants and Ecosystems ; Microbial Ecology and Applied Microbiology ; Palaeontology
• Term: from 2018 to 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 392246132

Since the middle of the 20th century, global temperature trends are rising. This warming is caused by a combination of natural factors and human activities and may have severe consequences for earths inhabitants and human society in particular. Thorough understanding of climate processes and their feedback mechanisms is essential to comprehend and face the impact of climate changes. Studies on past climate conditions play an important role as they demonstrate how temperature changes have affected the earth previously. Such knowledge can be obtained from the remains of organisms that lived in the past, as they can provide information on the conditions at the time of their origin. Some organisms modify their lipid composition as an adaptation to changing growth conditions. Analysis of such lipids in ancient sediments could therefore provide information on the conditions at the time of deposition, but unfortunately, the number of successful applications is still very limited. Recently, long chain alkyl diols were identified as a group of lipids whose distribution seems to be affected by water temperature - 1,13- and 1,15-diol distributions in sea surface sediments show a strong correlation with the annual temperature of the overlaying surface waters. Subsequent studies using diols in combination with other climate reconstruction methods have confirmed the potential of these lipids for the reconstruction of past temperatures but also indicated differences with other methods. Differences may be expected as each method may register temperatures of a specific season or water depth. However, diol distributions could also be affected by factors other than temperature, and this would affect their reliability for climate reconstruction. Hence, it would be obvious to test which environmental factors affect the diol distribution, but this is severely hampered by the fact that the biological sources of these lipids are yet unknown. The proposed project aims to identify and isolate the biological sources of diols in marine environments, and to test which growth conditions affect the diol composition. The Mediterranean Sea is an area known to contain diols and, subsequently, their biological sources. Water samples from this sea will be collected at different times in a year, and analyzed on the presence of diols, while DNA analyses will provide information on the of micro-organism composition. Using this knowledge, possible diol producers will be isolated from the water samples, cultured, and analyzed on their lipid composition. Next, diol producing strains will be grown at different temperatures and under different nutrient and salinity conditions, to determine the effect of these environmental conditions on their diol distributions. The results of this project may constrain the use of diols for sea surface temperature reconstruction, provide valuable background information, and thereby improve their use for climate reconstruction studies.

• DFG Programme: Research Grants
• Co-Investigator: Professor Dr. Volker Thiel